Advances in Geosciences

Published by European Geosciences Union
Online ISSN: 1680-7359
Publications
The El Niño event of 1997/1998 caused dry conditions over the Indonesian area that were followed by large scale forest and savannah fires over Kalimantan, Sumatra, Java, and parts of Irian Jaya. Biomass burning was most intense between August and October 1997, and large amounts of ozone precursors, such as nitrogen oxides, carbon monoxide and hydrocarbons were emitted into the atmosphere. In this work, we use satellite measurements from the Global Ozone Monitoring Experiment (GOME) sensor to study the teleconnections between the El Niño event of 1997 and the Indonesian fires, clouds, water vapour, aerosols and reactive trace gases (nitrogen dioxide, formaldehyde and ozone) in the troposphere.
 
SO 2 vertical column densities as retrieved from GOME for 13 December 2000 (top-left). Representing a coherent ensemble of matching forward trajectories, three trajectories are plotted released at the Popocatepetl at altitudes from 5 to 7 km and durations of 24 h. The other panels show SO 2 vertical column densities, cloud fraction and cloud top height on 15 December 2000.  
SO 2 vertical column densities of the eruption of El Reventador, Ecuador for 2, 3 and 5 November 2002, as measured by GOME. Trajectories were released from 4 km to 20 km in steps of 2 km using durations of 24 h. The trajectories matching the plume are coloured in white. Bottom-right: Longitudinal crosssection of the forward trajectories released for the El Reventador eruption at 3 November 2002. Trajectories were released at 06:00 UTC from 4 to 20 km above sea level in steps of 2 km using durations of 24 h. The vertical wind shear between 14 km and 16 km can be well recognized.  
SO 2 vertical column densities derived from GOME-2 for the eruption of El Reventador/Ecuador for 7 May 2007. Backward trajectories calculated for this case indicate an emission height of 6 km.  
SO 2 vertical column densities retrieved from SCIAMACHY for the eruption of Sierra Negra on the Galapagos Island for 23 and 24 October 2005.  
Volcanic eruptions can emit large amounts of rock fragments and fine particles (ash) into the atmosphere, as well as several gases, including sulphur dioxide (SO2). These ejecta and emissions are a major natural hazard, not only to the local population, but also to the infrastructure in the vicinity of volcanoes and to aviation. Here, we describe a methodology to retrieve quantitative information about volcanic SO2 plumes from satellite-borne measurements in the UV/Visible spectral range. The combination of a satellite-based SO2 detection scheme and a state-of-the-art 3D trajectory model enables us to confirm the volcanic origin of trace gas signals and to estimate the plume height and the effective emission height. This is demonstrated by case-studies for four selected volcanic eruptions in South and Central America, using the GOME, SCIAMACHY and GOME-2 instruments.
 
(a) Conceptual schematic of the EPAC sensor. The lower face of the sensor is earthed, with the upper face providing a sensing electrode, insulated from earth. The area of -3 2 the electrode is 8x10 m . When exposed to the atmospheric potential gradient, a voltage is 
Electricity in the atmosphere provides an ideal topic for educational outreach in environmental science. To support this objective, a simple instrument to measure real atmospheric electrical parameters has been developed and its performance evaluated. This project compliments educational activities undertaken by the Coupling of Atmospheric Layers (CAL) European research collaboration. The new instrument is inexpensive to construct and simple to operate, readily allowing it to be used in schools as well as at the undergraduate University level. It is suited to students at a variety of different educational levels, as the results can be analysed with different levels of sophistication. Students can make measurements of the fair weather electric field and current density, thereby gaining an understanding of the electrical nature of the atmosphere. This work was stimulated by the centenary of the 1906 paper in which C.T.R. Wilson described a new apparatus to measure the electric field and conduction current density. Measurements using instruments based on the same principles continued regularly in the UK until 1979. The instrument proposed is based on the same physical principles as C.T.R. Wilson's 1906 instrument. The constructional details of the instrument are provided here.
 
1° PPI scan of reflectivity [dBZ] observed by POLDIRAD at 1659 UTC. The data is interpolated onto the WRF model grid for evaluation.
Simulated reflectivity for Lin at 19 UTC (upper left), and WSM6 (upper right), WSM5 (lower left) and Thompson (lower right) at 20 UTC, along with histogram of frequency of occurrence of reflectivity values.
RHI scans of observations (upper left), Lin (upper right), WSM6 (middle left), WSM5 (middle right) and Thompson (bottom).
Simulations of a squall line system which occurred on 12 August 2004 near Munich, Germany are performed using a fine grid version of the Weather Research and Forecasting (WRF) model with five different microphysical schemes. Synthetic dual polarization observations are created from the model output and compared with detailed observations gathered by the DLR polarimetric radar POLDIRAD located near Munich. Synthetic polarimetric radar scans are derived from the model forecasts employing the polarimetric radar forward operator SynPolRad. Evaluations of the microphysical parameterization schemes are carried out comparing Plan Position Indicator (PPI) and Range Height Indicator (RHI) scans of reflectivity and the spatial distribution of hydrometeor types. The hydrometeor types are derived applying a hydrometeor classification scheme to the observed and simulated polarimetric radar quantities. Furthermore, the Ebert-McBride contiguous rain area method of verification is tested in a variety of ways on the reflectivity output from the simulations. It is found that all five schemes overestimate reflectivity in the domain, particularly in the stratiform region of the convective system. All four schemes including graupel as a hydrometeor type produce too much of it. Differences are seen among the schemes in their depiction of reflectivity in the convective line and their representation of radar bright bands.
 
Covariance C(T − o2 , p|τ ) of the negative 90 @BULLET E Alpine torque with pressure in hPa in fall at z=500 m at (a) τ =−1 day and (b) τ =2 days but with the sign reversed to obtain the " observed " pressure fields; topography dark; contour interval 0.5 hPa; negative values shaded.  
Typical events of torques exerted by the Alps are analysed by correlating flow observations in the Mediterranean with these torques. More specifically, events with positive torques with respect to the "rotation axis" at 90° E, 0° N in fall are selected. A trough forms above the western Mediterranean during such an event with a ridge in the west. A separate low pressure system is induced in the lee of the Alps which moves then eastward with the upper-level trough. A linear forecast equation based on potential temperature changes reveals that this Alpine "lee cyclone" is mainly due to warm air advection east of the trough. Precipitation is discussed as well.
 
We are reporting the technological and scientific objectives of the MEM project. The MEM project has been activated in the INGV Observatory of L'Aquila to create in Central Italy a network of observatories in order to monitoring the electromagnetic signals in the frequency band [0.001 Hz–100 kHz]. Some examples of the instrumentation developed in the frame of the project are reported. An innovative technique, based on the wide band interferometry is proposed to obtain detailed information concerning the several detected electromagnetic sources. Moreover, data from each station will be elaborated to investigate different sectors as the structure of ground electric conductibility, the electromagnetic phenomena connected with seismic activity, the separation of the electromagnetic fields originated in the Earth's interior and the electromagnetic phenomena originated in the magnetosphere, in the ionosphere and in the Earth-ionosphere cavity.
 
Topography of the Salerno Bay shelf and coast and location of gravity cores. Dashed line bounds the Bonea stream catchments.
Results of grain size analysis on T and F sandy layers of cores C1064, C853, C839 and C6 are plotted on a modified Shepard (1954) diagram. The grain size classes represented at triangle vertex are from Wentworth (1922) scale as follows: coarse to fine sand (500 microns>grain size>125 microns), very fine sand (125 microns>grain size>63 microns), mud=(grain size<63 microns).  
Very high resolution seismic lines (Sub-bottom Chirp) shot normally to the Bonea stream coast show the extention of tempestite deposits..  
The shallow marine Late Holocene wedge of the northern Salerno Bay shelf (Southern Tyrrhenian Sea) discloses the presence of four decimetric shelf-tapering sand beds. Their internal features, depicted by cores analysis and their stratigraphic position, revealed by VHR seismic investigations, inferred sandy layers as being the result of flash deposition, storm controlled, thus episodic. Stratigraphic correlations among cores lead to constrain sandy layers deposition to storm events falling in the 11th, 16th, 19th and 20th centuries. A certain attribution of the most recent event bed to the major cloudburst that hit the Salerno region in 1954A.D. and resulted in a disastrous flood of the Bonea stream, was formerly achieved. A tentative link with two sea-storms that occurred in the 1544A.D. and in the 1879A.D. and well documented by historical sources is here proposed to explain the deposition of the two previous event beds. The deposition of these sandy layers must be related to major storm events, since their preservation in the stratigraphic record is not common. Lithostratigraphic and textural differences between flood and sea-storm emplacement emerge from the study of sandy layers in cores and point to a prevalence of sea-storm deposits in the middle shelf compared to flood deposits. Seismic stratigraphic evidence lead us to suppose that the style of episodic flash deposition has been running on for the last 2-3kyr and is probably linked to a climatic trend of the region.
 
The most important hail event recorded in the region of the Ebro Valley (NE Spain) in 2004 was the 11 September episode. Large hailstones (some of them with a diameter of over 30 mm) caused important damages in agriculture and properties. The hail event affected an area of 3848 ha and was caused by several multicellular systems. The aim of this paper is the analysis of the associated convective structures using the meteorological radar as well as the MM5 mesoscale model, thermodynamic data and a hailpad network. To achieve this end, the new hailstorm analysis tool RHAP (Rainfall events and Hailstorms Analysis Program) has been applied. It identifies tracks and characterises precipitation systems and convective cells, taking into account 2-D and 3-D structures. The event has also been studied with the TITAN software (Thunderstorm Identification, Tracking, Analysis and Nowcasting) in an attempt to compare both methods. Results show that the episode had a strong convective activity with CAPE values over 4000 J/kg and with hail-forming cells characterised by VIL (Vertical Integrated Liguid) exceeding 40 kg/m<sup>2</sup>, VILD (VIL density) over 4 g/m<sup>3</sup>, HP (Hail Probability) of 100% and SHP (Severe Hail Probability) of over 75%. The hail cells evolved into multicellular systems that lasted between 70 and 90 min. Finally, the comparison of RHAP and TITAN has shown significant correlations between methods.
 
Large-scale hydrological modelling has become increasingly wide-spread during the last decade. An annual workshop series on large-scale hydrological modelling has provided, since 1997, a forum to the German-speaking community for discussing recent developments and achievements in this research area. In this paper we present the findings from the 2007 workshop which focused on advances and visions in large-scale hydrological modelling. We identify the state of the art, difficulties and research perspectives with respect to the themes "sensitivity of model results", "integrated modelling" and "coupling of processes in hydrosphere, atmosphere and biosphere". Some achievements in large-scale hydrological modelling during the last ten years are presented together with a selection of remaining challenges for the future.
 
Two major earthquakes near the Central Kuril Islands (Mw=8.3 on 15 November 2006 and Mw=8.1 on 13 January 2007) generated trans-oceanic tsunamis recorded over the entire Pacific Ocean. The strongest oscillations, exceeding several meters, occurred near the source region of the Kuril Islands. Tide gauge records for both tsunamis have been thoroughly examined and numerical models of the events have been constructed. The models of the 2006 and 2007 events include two important advancements in the simulation of seismically generated tsunamis: (a) the use of the finite failure source models by Ji (2006, 2007) which provide more detailed information than conventional models on spatial displacements in the source areas and which avoid uncertainties in source extent; and (b) the use of the three-dimensional Laplace equation to reconstruct the initial tsunami sea surface elevation (avoiding the usual shallow-water approximation). The close agreement of our simulated results with the observed tsunami waveforms at the open-ocean DART stations support the validity of this approach. Observational and model findings reveal that energy fluxes of the tsunami waves from the source areas were mainly directed southeastward toward the Hawaiian Islands, with relatively little energy propagation into the Sea of Okhotsk. A marked feature of both tsunamis was their high-frequency content, with typical wave periods ranging from 2–3 to 15–20 min. Despite certain similarities, the two tsunamis were essentially different and had opposite polarity: the leading wave of the November 2006 trans-oceanic tsunami was positive, while that for the January 2007 trans-oceanic tsunami was negative. Numerical modeling of both tsunamis indicates that, due to differences in their seismic source properties, the 2006 tsunami was more wide-spread but less focused than the 2007 tsunami.
 
The observables of the GOCE three-axis gradiometer are taken in time, along the orbit and, in the timewise proposal, filtered to stay in the measurement bandwidth, i.e. in the frequency interval between 0.005 and 0.1Hz. As a consequence, the resulting “observable" is a convolution of the original data stream with a time-wise weighting kernel. In other words, we cannot assume that the observations are point-wise evaluations of any function and so, in a spacewise approach, any averaging or interpolating operation to obtain gridded spatial data has little sense. The problem is therefore to model correctly the observational functionals, including the correlation along the orbit. This can be done by exploiting theWiener filter theory, using the prior knowledge of a geopotential model and the power spectral density (PSD) of the measurement error. A numerical simulation from the EGM96 model (degrees between 50 and 300) is performed, showing that the along track Wiener filter produces T rr spatialized observables with an error standard deviation of the order of 5 mE. A covariance function of the estimation error is also provided by the Wiener filter theory. The use of these filtered observables in a space-wise approach allows for the reconstruction of the gravity field in terms of spherical harmonics up to degree 200. Key words. Satellite gradiometry, space-wise approach, measurement bandwidth, Wiener filter
 
Stratigraphical and geometrical settings, seepage finite element model and hydraulic and geotechnical parameters adopted in the analyses. Figure 2. Stratigraphical and geometrical settings, seepage finite element model and hydraulic and geotechnical parameters adopted in the analyses. 
Test 2b. A) Pore pressure distribution, flux vectors, and critical failure surface at time step 22 (16:30 on 16 November) for 15 m and 30 m-long models; B) rainfall Figure intensity 3. Test 2b. and A) pore Pore pressure pressure changes distribution, versus time flux vectors, for all the and three critical soils failure at a horizontal surface at distance of 7.5 m from the downslope model boundary. time step 22 (16:30 on 16 November) for 15 m and 30 m-long models; B) rainfall intensity 9 and pore pressure changes versus time for all the three soils at a horizontal distance of 7.5 m 
On 14-16 November 2002 the North Italy was affected by an intense rainfall event: in the Albaredo valley (Valtellina) more than 200 mm of rain fell triggering about 50 shallow landslides, mainly soil slips and soil slip-debris flows. Landslides occurred above the critical rainfall thresholds computed by Cancelli and Nova (1985) and Ceriani et al. (1994) for the Italian Central Alps: in fact the cumulative precipitation at the soil slips initiation time was 230 mm (in two days) with a peak intensity of 15 mm/h. A coupled analysis of seepage and instability mechanisms is performed in order to evaluate the potential for slope failure during the event. Changes in positive and negative pore water pressures during the event are modelled by a finite element analysis of water flow in transient conditions, using as boundary condition for the nodes along the slope surface the recorded rainfall rate. The slope stability analysis is conducted applying the limit equilibrium method, using pore water pressure distributions obtained in the different time steps by the seepage analysis as input data for the calculation of the factor of safety.
 
Rain-gauge accumulated precipitation (mm) from 14th Sept. 06UTC to 15th Sept. 06UTC. (Courtesy of DIR Sud-Est-Météo-France). 
ARPEGE analysis for 14 September 00:00 UTC: 850 hPa equivalent potential temperature (K), 850 hPa wind arrows and altitude of the 1.5 pvu surface (isolines, m). 
ARPEGE analysis for 14th Sept. 00UTC: 850 hPa equivalent potential temperature (K), 850 hPa wind arrows & altitude of the 1.5pvu surface (isolines, m). 
Simulation domains with topography. 
Simulation domains with topography. 
A preliminary study of the 14 September 2006 heavy rainfall episode in Corsica is presented. Two sets of initial and coupling fields were used to run the French non-hydrostatic mesoscale model, MESO-NH. Three interactive 2-way nested domains were used, having 150×120, 150×150 and 125×200 grid points and 50 km, 10 km and 2 km mesh sizes. 50 vertical levels were defined. From ground level to 2000 m, the vertical resolution was 60 m, whereas it was 600 m above. Convection was parameterized for the coarser and intermediate domains and assumed to be explicitly resolved for the 2 km grid. At large scale, the situation is well represented by both simulations but, at the fine scale, they present significant differences. Comparison with the observations did not allow the two simulations to be discriminated. Even though the main high-level dynamical ingredients usually associated with rain storms were present in both simulations, their fine scale evolution was not reproduced well. Near the surface, there were significant differences between the two simulations. Vertical motion fields associated with convective phenomena were different in the innermost domain. A cold pool acting as a warm front off the east coast was associated with the main rainfall area over the sea in one simulation whereas in the second one, it seemed that the Corsican mountains acted as a barrier, leading to inland rainfall. This preliminary study gives perspectives for future sensitivity tests. For example, an investigation is planned of the influence of the high level dynamics, the SST and a better description of the orography.
 
Multiple proxy records (tree-ring, coral, ice and documentary) were examined to isolate ENSO signals associated with both phases of the phenomenon for the period A.D. 1525-2002. To avoid making large-scale inferences from single proxy analysis, regional signals were aggregated into a network of high-resolution records, revealing large-scale trends in the frequency, magnitude and duration of pre-instrumental ENSO using novel applications of percentile analysis. Here we use the newly introduced coupled ocean-atmosphere ENSO index (CEI) as a baseline for the calibration of proxy records. The reconstruction revealed 83 extreme or very strong ENSO episodes since A.D. 1525, expanding considerably on existing ENSO event chronologies. Significantly, excerpts of the most comprehensive list of La Niña events complied to date are presented, indicating peak activity during the 16th to mid 17th and 20th centuries. Although extreme events are seen throughout the 478-year reconstruction, 43% of the extreme ENSO events noted since A.D. 1525 occur during the 20th century, with an obvious bias towards enhanced El Niño conditions in recent decades. Of the total number of extreme event years reconstructed, 30% of all reconstructed ENSO event years occur post-1940 alone suggesting that recent ENSO variability appears anomalous in the context of the past five centuries.
 
Main orographic systems of Catalonia (NE Spain) and locations mentioned within the text.
Probability thresholds and outputs of the analogous tech- nique.
Stations with available pluviometric data. Blue ones are involved into the analogous process selection.
Different domains used in analogous technique. 
Between the 16 and 18 October 2003, some amounts of precipitation greater than 225mm and sea waves higher than 8.5m were recorded in Catalonia (NE Spain) and near its coast. Some rivers in the NE of the region were overflowed and the sea swell produced several damages near the coast. In order to analyse this case and to improve the forecasting of events like this, two methodologies have been applied: one deterministic and another one, probabilistic. The deterministic analysis has been made by using the MM5 mesoscale model. A 48 h simulation has been designed for three domains connected with two way nesting and having 54, 18, 6 km horizontal grid resolution and vertical resolution of 23 levels, and it has been initialised with the NCEP Analyses. The simulation suggests that orography played an important role on the precipitation generation (maxima were located where the wind at low levels impinged on the mountain ranges perpendicularly). The strong pressure gradient produced in the North of Catalonia and West part of the Gulf of Lyon, was the responsible of the great marine alteration. On the other hand, the 6 km resolution precipitation forecast for Catalonia is accurate, since it shows a spatial distribution and amounts quite similar to the observations obtained from 315 automatic rain gauges. The analogous technique applied here, considers the meteorological situations similar to the current one, in terms of the 850 and 1000 hPa geopotential fields at 00:00 UTC and 12:00 UTC from the NCEP/NCAR meteorological reanalysis for the period 1958–2003. Two windows have been considered, the first one from 60° N to 30° N and from 30° W to 30° E, and the second one, centred in Catalonia, from 45° N to 37.5° N and from 5° W to 10° E. The best 100 analogous have been selected and the comparison of the results with those obtained for other heavy rainfall events has been also done.
 
The greatest earthquakes in Algarve. 
The water height in 1755 tsunami: inverted model 
The 1755 Lisbon earthquake, which reached a magnitude of 8.5, remains the most powerful and destructive to hit Europe so far. Within minutes, many lives were lost, populations displaced, livelihoods, homes and infrastructures were destroyed. Although frequently associated to the city of Lisbon, one of the most important European cities at the time, this earthquake caused similar damage and casualties, if not greater, in the southwest of the Algarve, where the seismic intensity was estimated at IX-X Mercalli Intensity Scale. Some time later a tsunami increased the number of victims and the amount of damage. In some locations the tsunami caused greater destruction than the earthquake itself. The tsunami hit both coasts of the North Atlantic; however, the more destructive damage occurred in the Portuguese coast, south from Lisbon, in the Gulf of Cadiz and in the Moroccan coast. The downtown of Lisbon was flooded by waves that reached a height of 6 m. The water flooded an area with an extension of around 250 m from the coast. In the Southwest part of Algarve the waves reached a height between 10 and 15 m and the flooded area was much larger. Through the analysis of recent research works on the assessment of the 1755 tsunami parameters and the interpretation of the more reliable historical documents, it is our intention to analyse the destructive power of the tsunami in the Algarve and delimit the flooded area. Using simple techniques of simulation it is our intention to assess the impacts nowadays of the occurrence of a tsunami similar to the one that hit the Algarve in 1755, which would probably affect a greater number of people, buildings and infrastructures. This assessment is an important instrument not only in terms of disaster preparedness but also for the integration of risk mitigation measures in land use planning.
 
Recent studies show a change, starting in 1998, in the behavior of the variation of the dynamical flattening of the Earth (J2), supposed to be constant (secular), and mainly due to the post glacial rebound effect. In this paper, we study to what extent this behavior can be correlated or not with the 18.6 year tide: with more than twenty years of tracking data on LAGEOS-1, that is to say more than a period of 18.6 years, this effect can now be separated from the secular variation. We use our theory of mean orbital motion, dedicated to studies of the long period effects on the orbital motion. We build one single arc of LAGEOS-1 from 1980 to 2002, which provides a continuous description of the orbital parameters. This is the great originality of our approach. We focus our attention on the ascending node of LAGEOS-1, and we show that the change observed in j<sub>2</sub> cannot be attributed to a statistical error due to a correlation, in short arcs results, between the secular variation of J<sub>2</sub> and the 18.6 year tide. The proof is based on the adjustment of amplitudes and phases of the long period tides, and on the shape of the residuals. Key words. secular variation of J<sub>2</sub> , 18.6 year tide, mean orbital motione
 
This study analyses the extreme event which took place on 4 November 1966, when a storm produced intense and persistent precipitation over northern and central Italy and an extreme surge in the northern Adriatic Sea, causing casualties and huge damages. Numerical simulations with a regional atmospheric model have been performed to reconstruct the phenomenology of the event. Results have been compared with observations. This study shows that the choice of the global fields for initial and boundary conditions is crucial for the quality of the reconstruction. The simulation is reasonably accurate if they are extracted from the NCEP re-analysis, while it is not satisfactory if ERA-40 data are used, though fields have a higher resolution in the ERA-40 than in the NCEP set of data. The internal physics of the model plays a smaller role in the reproduction of the dynamics of the event.
 
Rimac delta base stratigraphy along Barranco-Chorrillos districts cliff (Figs. 3 and 4, where "28" is sited): Beds and lenses of conglomerate, sand and clay alluvial sediments. The buss at the bottom of the cliff serves as a scale. This photo is near the site where Espinosa et al. (1977) estimated 0.7 g ground acceleration at the crown.
Color coded of October-31974 earthquake macroseismic data (circles) in MSK scale values. Black triangles are boreholes or pits used for geotechnical information. The thin-black lines are district limits, and the smallblack numbers are the district codes used in the upper right table: Name of the districs. Open circles (blue) represent IGP facilities or strong motion stations.
Post-disaster reconstruction management of urban areas requires timely information on the ground response microzonation to strong levels of ground shaking to minimize the rebuilt-environment vulnerability to future earthquakes. In this paper, a procedure is proposed to quantitatively estimate the severity of ground response in terms of peak ground acceleration, that is computed from macroseismic rating data, soil properties (acoustic impedance) and predominant frequency of shear waves at a site. The basic mathematical relationships are derived from properties of wave propagation in a homogeneous and isotropic media. We define a Macroseismic Intensity Scale IMS as the logarithm of the quantity of seismic energy that flows through a unit area normal to the direction of wave propagation in unit time. The derived constants that relate the IMS scale and peak acceleration agree well with coefficients derived from a linear regression between MSK macroseismic rating and peak ground acceleration for historical earthquakes recorded at a strong motion station, at IGP&apos;s former headquarters, since 1954. The procedure was applied to 3-October-1974 Lima macroseismic intensity data at places where there was geotechnical data and predominant ground frequency information. The observed and computed peak acceleration values, at nearby sites, agree well.
 
Standardized anomalies of (a) sea surface temperature (SSTA) of the El Niño 1+2 Region and (b) Tumaco for the 19612002 period. Red (blue) colors indicate positive (negative) anomalies caused by El Niño (La Niña) events.
Standardized anomalies of air temperature (Granja El Mira), for the 1969–2002 period. Red (blue) colors indicate positive (negative) anomalies caused by El Ni no (La Ni na) events. 
Hydro-climatic Balance (from Palmer, 1968) of Tumaco (Granja El Mira). During the first and last months of an average year there is storage of water on the soils. The first semester (rainiest in- dicated by the blue line) has excess of water while during the second semester (less rainy) there is more consumptions (evo-transpiration) that could cause sever droughts. 
Oil palm tree life cycle stages from the initial stage (t=0), to the fruit harvest (t=40 months). 
Highest cross-correlation found ( r =0.86) between climatic and agro-climatic anomalies (1992–2002) and production anomaly (1995–2002) at Granja El Mira experimental Lot-Tumaco, Colombia. The meteorological variability of July 1992 affected the Jan- uary 1995 oil palm production (2.6 years delay), and so on. 
Although the relationship between ENSO events and oceanographic and meteorological conditions of Southwestern Colombia is well-known, very little work has been done to assess the related socio-economic impacts. This is the first effort made to determine the effect of such events on local climate and the impact of this variability on oil palm tree ( Elaeis guineensis ) production in the Tumaco municipality, which is located on Colombia&apos;s Pacific coast. First, we studied the correlation between sea surface temperature anomalies (SSTA) in the various El Niño regions and those observed off Tumaco. Next, we scrutinized the ENSO impact on regional climatic indicators, e.g. active solar radiation (hrs/day), air temperature (°C), and rain (mm). Finally, we analyzed the relationship between ENSO, Tumaco climate variability, and oil palm production (tons/hectare-month). Hours of active radiation increased (decreased) under El Niño (La Niña) conditions, as did average monthly precipitation rates and air temperature. ENSO-related climatic variability also had an important effect on the different developmental stages of the oil palm tree, thereby affecting its production. The worst scenario was found during La Niña, when reduced intensity of the rainy season (second semester) caused severe droughts in the region.
 
Location of the sampling stations for diet analysis of hake, oceanographic coastal station and coverage of scientific cruises for biomass estimations and oceanographic profiling in the northern Humboldt Current ecosystem (HCE). 
Size-related groups of hake based on diet composition as derived by a cluster analysis (Euclidean distance, average grouping) in the Northern HCE. Significant differences between groups were confirmed by an ANOSIM procedure. Percentage of contribution of characteristic prey taxa to the similarity within each hake size group is indicated in brackets. 
Relative importance of prey categories in the diet of hake. Changes in general prey groups with size are shown in the left panel. According to discontinuities in RI values, prey categories can be characterised as dominant, secondary or occasional in the hake size groups derived from the multivariate analysis (right panels). 
Monthly variability (October 1995 to November 2002) of: (a) Marine physical signal, (b) Biomass estimations of main fish prey species, (c) Relative Importance (RI) of most abundant prey taxa in the diet of hake (251–450 mm TL size group), (d–e) Prey spectrum diversity (Hill’s N1 and N2 numbers), and (f) Number of prey taxa per stomach. Period of highest SSTA is indicated with a shadowed grid. Months with less than 30 analysed stomachs were not considered. 
Temporal changes of mean total length and fullness index ( FI ) of hake. Error bars are 95% confidence intervals. 
Hake ( Merluccius gayi peruanus ) predation plays an important role in the dynamics of the Humboldt Current ecosystem (HCE). Changes in the hake trophic habits associated with physical variability are expected to impact prey populations and to propagate through the food web. Time series (1995–2002) of (a) stomach contents of hake, (b) biomass estimations of fish prey species of hake, and (c) depth of the 15°C isotherm was analysed with the aim of exploring the impacts of El Niño 1997–1998 on the diet of hake. Biomass estimations of fish prey species were used to indicate resource availability, and depth of the 15°C isotherm to represent variability associated with the ENSO cycle in the physical environment of hake. The richness of prey species increased during the months when 15°C isotherm reached its deepest position, supporting the hypothesis of increased biodiversity (tropicalization) of the HCE during El Niño events. An increased variability in stomach fullness of hake was detected after 1999 which could indicate high heterogeneity in the food supply as a consequence of impacts of the warm event in the biotic community structure of the HCE, a physiological impairment of hake or an effect of the abrupt reduction in the mean total length of hake, postulated as a compensatory response to fishery pressure. Hake can be characterized as an opportunist predator according to the observed changes in its diet during 1995–2002. Overall, the diet of hake in the northern HCE exhibited transitory (e.g. increased richness of prey species in the stomach contents) and medium term (e.g. increased variability in feeding activity) responses associated with El Niño 1997–1998, which should be incorporated both in population dynamics and food web analyses.
 
Precipitation partition into convective and stratiform components. SW region Spain, hydrological year 1998. The last grey bar (R=148.75 mm/6h) corresponds to an extremely intense precipitation event that took place in Huelva on 27/9/1997 with no d consequences. The first grey bar on the "convective area" (R=33.25 mm/6h) correspon three rainy episodes that happened on Huelva, Sevilla and Badajoz at different stages o hydrological year Fig. 2. Precipitation partition into convective and stratiform components. SW region of Spain, hydrological year 1998. The last grey bar (R=148.75 mm/6 h) corresponds to an extremely intense precipitation event that took place in Huelva on 27 September 1997 with no dramatic consequences. The first grey bar on the "convective area" (R=33.25 mm/6 h) corresponds to three rainy episodes that happened on Huelva, Sevilla and Badajoz at different stages of the hydrological year.
Q vector divergence [ ] at 500 hPa level. 0000 UTC 6/11/1997. Spatial resolution: 0.5ºx0.5º.
Potential vorticity anomalies (in Potential Vorticity Unit, Fig. 7. Q vector divergence [ kP a m − 2 s − 1 ] at 500 hPa level. 1PVU=10 − 6 Km 2 s − 1 Kg − 1 ) at the 330 K isentropic surface. Figure 00:00 UTC 7: 6 Q November vector 1997. divergence Spatial resolution: [ kPa 0.5 ◦ × m 0 . 5 − ◦ 2 . s − 1 ] at 00:00 500 Figure UTC hPa 6 November 8: level. Potential 1997. 0000 Spatial vorticity UTC resolution: 6/11/1997. anomalies 0.5 ◦ × 0 . 5 ◦ . Spatial (in Potenti at the 330 K isentropic surface. 0000 UTC 6/11/1 resolution: Badajoz heavy 0.5ox0.5o. rain event on 6 November 1997 was asso- and ECMWF for the reanalysis data. The Ministerio de Educación ciated with predominant convective regime. This technique, y Ciencia supported this study through the DINPRE (DINámica de based on statistical properties of in situ rain dataset, allows la PREcipitación) project (CGL2004-05187-C03-01/CLI). to identify convective systems without using satellite images and establish the main features of the two different modes of Edited by: S. C. Michaelides precipitation. Reviewed by: two anonymous referees A thermodynamic analysis shows that this rainy event was not associated with thermally unstable conditions. Since References these indices do not exhibit significant values, we can state that the dynamic instability played a fundamental role in the Houze, R. A.: Cloud Dynamics, Internatonal Geophysics Series, development of a MCS in Badajoz. The strong convection Vol. 53, Academic Press, 573 pp., 1993. related to the detected dynamic instability structures, along Houze, R. A.: Stratiform precipitation in regions of convection: with large amounts of moisture advected by a trough affect- A meteorological paradox?, B. Am. Meteorol. Soc., 78, 2179– ing IP, were ultimately responsible for the observed precipi- 2196, 1997. tation rates. Jusem, J. C. and Atlas, R.: Diagnostic evaluation of vertical mo- tion forcing mechanisms by using Q-vector partitioning, Mon. Finally, backward trajectories by using the Lagrangian Weather Rev., 126, 2166–2184, 1997. model FLEXPART6.2 provide a detailed and new perspec- Lang, S., Tao, W. K., Simpson, J., and Ferrier, B.: Modeling of tive for the analysis of MCSs. The assessment of the ori- convective – stratiform precipitation processes: Sensivity to par- gin and the trajectories of different air masses allows a better titioning methods, J. Appl. Meteor., 42, 505–527, 2003. understanding of hazardous rainfall episodes and provides a Rodrıguez-Puebla, C., Encinas, A. H., Nieto, S., and Garmendia, J.: helpful tool for forecasting and warning against floods and Spatial and temporal patterns of annual precipitation variability potential damages. over the Iberian peninsula. Int. J. Climatol., 18, 299–316, 1998. Rodrıguez-Puebla, C., Encinas, A. H. and Sáenz, J.: Winter precip- Acknowledgements. The authors wish to thank the National Me- itation over the Iberian peninsula and its relationship to circula- teorological Institute of Spain for providing the precipitation data tion indices, Hydrol. Earth Sy. Sci., 5, 233–244, 2001. 
Potential vorticity anomalies (in Potenti at the 330 K isentropic surface. 0000 UTC 6/11/1 Fig. 8. Potential vorticity anomalies (in Potential Vorticity Unit, 1PVU=10 −6 Km 2 s −1 Kg −1 ) at the 330 K isentropic surface. 00:00 UTC 6 November 1997. Spatial resolution: 0.5 • ×0.5 • .
The flooding episode of November 1997 in Badajoz was one of the most dramatic catastrophes in Spain: as a result, there were 21 fatalities and huge financial damages. The main purpose of this work is to assess the prevailing synoptic conditions as well as detailing the mesoscale effects by means of moisture sources and dynamic and thermodynamic instability analysis involved in the November 1997 Spanish severe weather episode. In order to achieve the above, this flood event is described in terms of moisture content evolution by means of individual particle simulation along 3-day back-trajectories. A Lagrangian model is applied in order to characterize the atmospheric particles involved in the focused case (localization, height and specific humidity) which give rise to sudden precipitation stream. Geopotential height and temperature fields were used to describe the synoptic situation. Thermodynamic indices, such as CAPE, SWEAT and KI, and dynamic parameters like potential vorticity anomaly at 330 K isentropic surface and Q vector divergence were also calculated in order to complete the analysis and to give a thorough weather frame taking into account the atmospheric instability. The results of this work suggest this flood event was due mainly to strong dynamic instability along with large amounts of moisture advected by a trough, while the thermodynamic instability played a secondary role. Finally, a new methodology based on a technique proposed by Tremblay (2005) has been developed in order to separate the precipitation into stratiform and convective components. It is evident that the event was associated with a predominant convective regime.
 
Error distribution for events of the Izmit aftershock hypocenter catalog as determined from the combined GTF and SABONET network. The error is given in kilometer for latitude, longitude and depth, respectively, and in seconds for the root mean square (RMS) value. Approximately 70% percent of all events have a location error better than 5 km in all three directions and a RMS better than 0.3 s. 
Izmit aftershock hypocenter catalog in map view and as depth section. All 7348 events shown here have locations errors better than 5 km in all directions. A predominant activity is observed along the entire segment ruptured by the mainshock except the westernmost portion below the Sea of Marmara (see text for details) forming a 20 km wide band of activity. Two major clusters of activity are observed in the Akyazi and Karadere-Düzce areas. The majority of events occurred between 5 and 15 km depth. Blue and red stars indicate the location of the Izmit and Düzce hypocenter, respectively. 
Relocated hypocenter catalog of Izmit aftershocks in the Akyazi and Karadere-Düzce area (western half of the rupture). Relative location accuracy improved by a factor of 6 compared to absolute hypocenters shown in Fig. 3 and allows to identify internal Fig. 4. Magnitude frequency of the Izmit aftershock hypocenter cat- structures within the seismically active area. Several planes as well alog as shown in Fig. 3. The magnitude threshold of completeness as cloud-type distribution of activity down to the resolved scale of of the joint GTF and SABONET network is Mc=1.1. Events down 300 Figure and 5: Relocated 400 m hypocenter for horizontal catalog of Izmit and aftershocks vertical in the direction, Akyazi and Karadere-Düzce respectively, area is to magnitudes as low as 0 are located and the largest magnitude con- observed (western half in of the both rupture). clusters Relative location (see accuracy text for improved details). by a factor of 6 compared to absolute hypocenters shown in Figure 3 and allows to identify internal structures within the seismically active area. Figure tained 4: Magnitude in the frequency catalog of is the 5.8. Izmit The aftershock inset shows hypocenter the catalog temporal as shown evolution in Figure 3. The for Several horizontal planes and as well vertical as cloud-type direction, respectively, distribution of is observed activity down in both to clusters the resolved (see text scale for of details). 300 and 400 m magnitude of Mc threshold during of completeness the Izmit of aftershock the joint GTF sequence. and SABONET Stable network values is Mc=1.1. for Events Mc down to magnitudes as low as 0 are located and the largest magnitude contained in the catalog is 5.8. The inset shows are the observed temporal evolution throughout of Mc during the first the Izmit ∼ 55 aftershock days. A sequence. significant Stable values decrease for Mc are not identified from the absolute locations (see Fig. 5). A clear which observed reasons of is Mc due throughout to is technical (see observed the Görgün reasons first ~55 after (see et days. al., Görgün Julian A 2007 significant et al., day 1 , 2007, for decrease 290 details). for details). which of Mc is is observed due to after technical Julian day 290 distributions distinction into are narrow observed planes in direct of activity vicinity. and more The cloud-type cloud-like distribution is justified down to the resolved spatial accuracy of 400 (vert.) m 300 m (hor.), i.e. features smaller than part of the Izmit rupture we abstain from further analysis that might exist but are not resolved. From the map view in of the seismicity in the Yalova area and refer to Karabulut Fig. 5 the existence of two main clusters of activity is clearly et al. (2002) and Aktar et al. (2004) who operated denser confirmed. The majority of events are observed between 6 networks in this area. Interestingly, Karabulut et al. (2002) and 16 km depth and only a smaller number occurred near observe a branching of the NAFZ into several streaks of ac- the surface in the Karadere-Düzce area. Thus, the overall tivity below the easternmost Sea of Marmara which was also hypocentral distribution as identified from absolute hypocen- obtained for this area from spatial clustering of similar after- ters (Fig. 3) is confirmed but its internal structure is signif- shock focal mechanisms (Bohnhoff et al., 2006). icantly refined. Moreover, the depth distribution was found being stable against different velocity models formerly proposed for the region (Bulut et al., 2007). 4 Relocation of Izmit aftershocks 
Karadere-Düzce area representing the easternmost part of the Izmit rupture. Topography was plotted after Fielding et al. (1999). Red dots indicate relocated hypocenters as shown in Fig. 5 that are subdivided into a narrow band of activity representing the down-dip extension of the Karadere fault in the west and a cloud of activity without internal structure down to the resolved scale of 400 m in the East. Fault plane solutions are from Bohnhoff et al. (2006) and include the four largest aftershocks of this segment, the Izmit subevent S2 (Tibi et al., 2001) and the Düzce mainshock. These six events all have an almost identical focal mechanism reflecting slip on an EW trending steeply northward dipping fault plane. This part of the NAFZ is interpreted to reflect a typical example for a fault barrier that was activated by the Izmit mainshock and re-ruptured and extended by the Düzce event after 87 days.
The most recent devastating earthquakes that occurred along the North Anatolian Fault Zone (NAFZ) in northwestern Turkey were the 1999 Izmit (Mw=7.4) and Düzce (Mw=7.1) events. In this study we present a catalog of Izmit aftershock hypocenters that was deduced from a network covering the entire 140 km long rupture of the mainshock. 7348 events with a location accuracy better than 5 km are analysed. Aftershocks were observed along the entire ruptured segment along a 20 km wide band of activity. Events are clustered in distinct regions and dominantly occur at 5 to 15 km depth. The eastern termination of the Izmit rupture is characterized by a sharp and steeply dipping boundary exactly where the Düzce mainshock initiated 87 days after the Izmit event. Relocation of the events using double-difference technology results in 4696 high-resolution hypocenters that allow resolving the internal structure of the seismically active areas with a resolution of 300 m (horizontal) and 400m (vertical). Below the Akyazi Plain, representing a small pull-apart structure at a triple junction of the NAFZ, we identify planes of activity that can be correlated with nodal planes of EW extensional normal faulting aftershocks. Along the easternmost Karadere-Düzce segment we identify the down-dip extension of the Karadere fault that hosted about 1 m of right-lateral coseismic slip. At the easternmost rupture we correlate a cloud-type distribution of seismic activity with the largest aftershocks in this area, a subevent of the Izmit mainshock and the Düzce mainshock that all have an almost identical focal mechanism. This part of the NAFZ is interpreted as a classical example of a seismic barrier along the fault.
 
Wavelet analysis of the sea surface temperature (SST) from Reynolds (NINO3 region) and of the zonal current (ZC) from the OSCAR data set (NINO4 region) for the period October 1992 to December 2010. (a, c) Wavelet power spectrum; black line represents the 90 % confidence spectrum. (b, d) Global wavelet spectrum, solid line is for the period 1992–1999 and dotted line is for the period 2000–2008. The dashed line indicates the 90 % confidence level for the period 1992–1999. (e) Averaged variance of the high-frequency variability relative to the low-frequency variability (i.e. (scale average[0.5–1.5] yr)/(scale average[2–7] yr) × 100) for: SST over the NINO3 region (dot-dash line, left scale), SST over the NINO4 region (dotted line, left scale) and ZC over the NINO4 region (solid line, right scale). Dashed line is the 90 % confidence spectrum associated with SST over the NINO3 region. (f) Howmoller for SST anomalies along the Equator for the period 1997–2001 (seasonal cycle from 1982 to 1996). 
First mode resulting from the SVD between wind stress and zonal current anomalies: (a) to (c) for the period from January 1993 to December 1999, and from (d) to (f) for the period from January 2000 to December 2008. Data are from SODA. The panels on the left-hand side and in the middle display the spatial pattern for zonal wind stress and zonal current, respectively. The panels on the right-hand side display the global wavelet spectrum of the time series associated with the first SVD mode: solid line for zonal wind stress (lower scale) and thick dotted line for zonal current (upper scale), dashed line is the 90 % confidence level for wind stress and thick dashed line is 90 % confidence level for zonal current. Contour interval (CI) = 0.015 units. Percentage of explained variance is indicated above each map. 
Same as Fig. 2 but for the SVD analysis between QuikSCAT wind stress (TXA) and OSCAR zonal current anomalies (ZCA) for the period from January 2000 to December 2004. 
(a–d) Composites of SST and wind stress anomalies, and (e–h) sea level and surface current anomalies at (a) , (e) 2 months before the mature phase of warm SST condition, (b) , (f) mature phase, (c) , (g) 2 months after the mature phase, and (d) , (h) 4 months after the mature phase. Contour interval (CI) = 0.15 units for SSTA and CI = 0.01 units for sea level anomalies. Units in ◦ C for SSTA and m for sea level anomalies. 
Maps of weighted skewness of the Reynolds SST anomalies for (a) the period 2000–2008 and (b) the period 1982–1999. CI = 0.2 units for SST. Units are ◦ C. 
Like the El Niño Southern Oscillation (ENSO), the near-annual mode is an air-sea coupled mode of the tropical Pacific that can emerge within a relatively cool mean state. It is documented here from satellite observations over the 2000-2008 period based on a covariance analysis between wind stress and zonal current anomalies. It is shown that near-annual variability is enhanced over the last decade. The signature of this mode consists of a zonal seesaw pattern for zonal current with westward (eastward) anomalous currents in the western (eastern) equatorial Pacific. A composite analysis allows identifying the peak and transition phases of this mode, particularly active over 2000-2004. It is suggested that the reduction of the interannual variability in the eastern Pacific over the last decade may be related to the enhancement of the near-annual mode.
 
Results of laboratory tests for both landslide sites. 
Study sites. A: Site 1,Uzzano landslide, B: Site 2, Massa and Cozzile landslide.
Site 1. Uzzano. Trend of the computed safety factor and rainfall data during the 2021 November 2000 event (1-factor of safety, 2-rainfall).
On the days 20-21 November 2000, a storm of exceptional intensity triggered over 50 landslides within the province of Pistoia in Tuscany (Italy). These failures are mostly of complex type, originating as rotational or translational landslides, and transforming into flows. Two of these landslides were investigated in this paper by modelling the ground water infiltration process, the pore water pressure variations, both positive and negative, and the effects of these variations on slope stability during the rainfall event. Morphometric and geotechnical analyses were carried out for both sites through a series of in-situ and laboratory tests, the results of which were used as input for the modelling process. In a first step the surface infiltration rate was simulated using a modified Chu (1978) approach for the Green and Ampt (1911) equations in case of unsteady rainfall together with a surficial water balance. A finite element seepage analysis for transient conditions was then employed to model the changes in pore water pressure during the event, using the computed infiltration rate as the ground surface boundary condition. Finally, once again using the data from the previous step as input, the limit equilibrium Morgenstern-Price (1965) slope stability method was applied to calculate the variations in the factor of safety during the event and thereby determine the most critical time of instability. In both sites this method produced a curve for the factor of safety that indicated that the most critical time for failure occurred a few hours after the peak of rainfall.
 
An objective evaluation of mesoscale simulations by the model-to-satellite approach is performed. The model-to-satellite approach consists in calculating brightness temperatures (BT) from model variables with a radiative transfer code. It allows to compare directly and quantitatively simulations and observations by calculating statistical scores. This method is detailed and used herein to objectively evaluate an ensemble of Meso-NH simulations of the Algiers 2001 flash flood. In particular, the improvement due to the grid-nesting is shown.
 
Schematic showing the 20 km model domain nested within the 60 km global model and the 4 km model domain nested within the 20 km domain and centred on Algiers. 
24-hour accumulations of the total precipitation amount for the period 12:00 UTC on the 9th November to 12:00 UTC on the 10th November for (a) the 60 km model, (b) the 20 km model and (c) the 4 km high resolution model. In each plot, the “X” marks the position of Algiers. 
Plots showing, for the 4 km model domain, (a) the unaltered domain orography, (b) the orography when a maximum height of 750 m is imposed and (c) the orography when a maximum height of 400 m is imposed. In each plot, the “X” marks the position of Algiers. 
Plots showing (a) the 24-hour accumulation of the total precipitation amount for the period 12:00 UTC on 9th November to 12:00 UTC on 10th November using the 4 km model with the original orography and for the same 24-hour period, (b) the difference in total precipitation amount between the control run and the run where the maximum orographic height is 750 m and (c) the difference in total precipitation amount between the control run and the run with a maximum orographic height of 400 m. In each plot, the “X” marks the position of Algiers. 
Plots showing (a) the 24-hour accumulation of the total precipitation amount for the period 12:00 UTC on 9th November to 12:00 UTC on 10th November using the 4 km model where L c and L f have their original values and for the same 24-hour period, (b) the difference in total precipitation amount between the control run and the run where L c and L f are halved and (c) the difference in total precipitation 
Between 18:00UTC on Friday 9th November and 12:00UTC on Saturday 10th November 2001 260mm of rainfall was recorded at Bouzareah, compared to the November average of just 96mm. This extreme rainfall resulted in landslides and flooding, causing immense damage to the Bab-el-Oued district of Algiers and affected the lives of more than 2000 people. In this paper, key results from a modelling study of this event using the UK Met Office Unified Model at global (60km), regional (20km) and national (4km) horizontal resolutions are described. In general, it is found that the event could be well forecast with increases in resolution leading to better predictions of both the distribution and intensity of the rainfall. The role of the local orography and latent heating are also discussed.
 
From 9 to 11 November 2001, intense cyclogenesis affected the northern coasts of Africa and more particularly the densely populated city of Algiers. During the morning of 10 November, more than 130 mm of precipitation was recorded at Bouzareah and resulted in mudslides which devastated the Bab-el-Oued district. This disaster caused more than 700 casualties and catastrophic damage. Like many other heavy rainstorms in the western Mediterranean, this event was associated with the presence of an upper-level trough materialized by a deep stratospheric intrusion and characterized by high potential vorticity values. In this study, the impact of this synoptic structure on the localization and intensity of the precipitation which affected Algiers is investigated using a potential vorticity (PV) inversion method coupled for the first time with the French non-hydrostatic MESO-NH model. A set of perturbed synoptic environments was designed by slightly modifying the extent and the intensity of the coherent potential vorticity structures in the operational ARPEGE analysis. It is shown that such modifications may have a strong impact on the fine-scale precipitation forecast in the Algiers region, thereby demonstrating the fundamental role played by the potential vorticity anomaly during this exceptional meteorological event.
 
Areal rainfall distribution of the storm of 8 July 2002.
Image from the NOAA satellite N16-AVHRR, λ = 11.5-12.5 µm.
We analyse the flood event of 8 July 2002 that caused overflows over portions of the lower reach of the Kifissos River/Canal. The storm covered only the lower basin area and was concentrated on the centre and the southwest side of Greater Athens. The issue that stirred the public opinion was whether the hydraulic works underway in lower Kifissos at that time were responsible for the overflows. We explore this issue with the hydrologic-hydraulic model of the Kifissos basin TELESIM. To shed light on the probable cause of the observed flooding, we ran TELESIM for two rain-field scenarios derived from the recorded point-rainfalls, computing flows for each scenario. Depth profiles for channel conditions without obstructions do not explain the observed flooding. With the channel taken as locally obstructed by flow-area reducing ramps plus bed-debris, estimated nominal overflows (bank-full level is threshold, but the water stays inside the channel) compare well with actual ones for the milder rainfall scenario. Hence, the simulations support as plausible the hypothesis that flow obstructions due to the construction caused the overflows.
 
Lectures during the summer school at Silkeborg Højskole offer a great possibility for discussions between students and researchers. Here Professor Jens Martin Knudsen is explaining why we should search for life on the planet Mars (Silkeborg Højskole, 2002; Photo by: M. Edinger). 
For the course we have installed telescopes that can be used to perform white light visual observing as well as H-alpha observing. (Silkeborg Højskole, 2002; Photo by: M. Edinger). 
The High School outreach programme is focused on the Sun, especially the use of SoHO and TRACE satellite data. The figure shows a giant Coronal Mass Ejection (CME) observed by the LASCO instrument onboard the SoHO spacecraft (for details see the SoHO homepage). Images like those are used extensively in our High School outreach programme.
During the summers of 2002, 2003 and 2004 a one-week public course on Astronomy took place at Silkeborg Folk High School in central Jutland, Denmark. The aim of the course was to offer a possibility for students to meet research scientists and discuss central scientific questions and their answers. Researchers from the Department of Physics and Astronomy at Aarhus University in Denmark took an active part in running this summer school and the course could also be seen as a part of the Department&apos;s general public outreach activities. The main aim of those activities is to: (1) show why research is important, (2) give students and children the possibility to meet people that do research, and (3) present authentic role models.
 
Locations of tide gauge recordings of the 2004 Sumatra tsunami on the Atlantic coast of South America.
Characteristic features of the 2004 Sumatra tsunami determined from tide gauge records on the Atlantic coast of South America.
The 2004 Sumatra tsunami propagated throughout the World Ocean and was clearly recorded by tide gauges on the Atlantic coast of South America. A total of 17 tsunami records were found and subsequently examined for this region. Tsunami wave heights and arrival times are generally consistent with numerical modeling results. Maximum wave heights of more than 1.2 m were observed on the coasts of Uruguay and southeastern Brazil. Marked differences in tsunami height from pairs of closely located tide gauge sites on the coast of Argentina illustrate the importance that local topographic resonance effects can have on the observed wave response. Findings reveal that, outside the Indian Ocean, the highest waves were recorded in the South Atlantic and not in the Pacific as has been previously suggested.
 
An extraordinary "rissaga" event (the local name for high-amplitude sea level oscillations) with 4–5 m of amplitude occurred on 15 June 2006 at Ciutadella (Menorca, Spain). In this paper we describe the rissaga event and propose that the meteorological mechanism responsible for it was an unusual pressure jump, associated with a convective squall line.
 
Comparison of observed (solid) and computed (dashed) tsunami waveforms at nine tide gauges and two ocean bottom pressure systems (DART) for the 2006 interplate Kurile earthquake. 
Comparison of observed (solid) and computed (dashed) tsunami waveforms at three tide gauges and one ocean bottom pressure system (DART) for the 2007 outer-rise Kurile earthquake. 
Bathymetry around Pacific and seven snapshots of the tsunami propagation of the 2006 Kurile tsunami. The snapshots are taken 2, 3, 4, 5, 6, 7, and 8 h after the origin time of the 2006 Kurile earthquake. An ellipsoid shows the large tsunami off Crescent City. 
The 2006 large interplate Kurile earthquake proved that the entire plate interface of the Kurile-Kamchatka subduction zone was strongly coupled from Hokkaido, Japan, to Kamchatka, Russia. The seismic moment of the 2006 Kurile earthquake estimated from ten tsunami waveforms is 3.1×1021 Nm (Mw=8.3). This estimate is consistent with the seismic moment estimated from the seismological data in the Global CMT catalog. The computed tsunami propagation indicates that scattering of the tsunami waves occurred at the shallow region near the Emperor Ridge. The computed tsunami propagation also indicates that large later tsunami waves observed at Crescent City is caused by the shallow region along the Mendocino Fracture Zone. The seismic moment of the 2007 outer-rise Kurile earthquake estimated from tsunami waveforms is 1.0×1021 Nm (Mw=8.0). This estimate is also consistent with the seismic moment in the Global CMT catalog.
 
We describe development of the 2006–2007 El Niño, which started late, ended early and was below average strength. Emphasis is on the interplay between large scale, low frequency (i.e., seasonal-to-interannual time scale) deterministic dynamics and episodic intraseasonal wind forcing in the evolution of the event. Efforts to forecast the El Niño are reviewed, with discussion of factors affecting its predictability. Perspectives on the contemporaneous development of an Indian Ocean Dipole Zonal Mode event in 2006 and possible influences of global warming on the ENSO cycle, which exhibited unusual behavior in the first decade of the 21st century, will also be presented.
 
The Sistema Idro-Meteo-Mare is an integrated meteo-marine forecasting chain for the Mediterranean basin. The recent update of the meteorological segment, based on the hydrostatic BOlogna Limited Area Model (BOLAM), gives the opportunity for a comparative verification study on a Mediterranean cyclone. The 10-12 December 2008 flood event in Rome has been chosen as case study. This disastrous event was claimed to be an extreme one by mass-media; however, its return time is shown here to be about 5 years. The Mediterranean cyclone responsible for the flood offers a tough case study in order to verify the model's ability in reproducing the evolution of meso-synoptic features in the Mediterranean environment. A qualitative comparison, employing satellite data and derived products, is performed. Results suggest that the upgraded model provides a more realistic representation of the cyclone warm sector - where the main rainfall peak took place - whereas the error in the cyclone trajectory and shape evolution is less affected by the BOLAM improvement.
 
The Centro di Ricerche Sismologiche (CRS, Seismological Research Center) of the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS, Italian National Institute for Oceanography and Experimental Geophysics) in Udine (Italy) after the strong earthquake of magnitude M=6.4 occurred in 1976 in the Italian Friuli-Venezia Giulia region, started to operate the Northeastern Italy Seismic Network: it currently consists of 17 very sensitive broad band and 18 simpler short period seismic stations, all telemetered to and acquired in real time at the OGS-CRS data center in Udine. Real time data exchange agreements in place with other Italian, Slovenian, Austrian and Swiss seismological institutes lead to a total number of about 100 seismic stations acquired in real time, which makes the OGS the reference institute for seismic monitoring of Northeastern Italy. The southwestern edge of the OGS seismic network stands on the Po alluvial basin: earthquake localization and characterization in this area is affected by the presence of soft alluvial deposits. OGS ha already experience in running a local seismic network in high noise conditions making use of borehole installations in the case of the micro-seismicity monitoring of a local gas storage site for a private company. Following the ML=5.9 earthquake that struck the Emilia region around Ferrara in Northern Italy on May 20, 2012 at 02:03:53 UTC, a cooperation of Istituto Nazionale di Geofisica e Vulcanologia, OGS, the Comune di Ferrara and the University of Ferrara lead to the reinstallation of a previously existing very broad band (VBB) borehole seismic station in Ferrara. The aim of the OGS intervention was on one hand to extend its real time seismic monitoring capabilities toward South-West, including Ferrara and its surroundings, and on the other hand to evaluate the seismic response at the site. We will describe improvements in running the Northeastern Italy Seismic Network, including details of the Ferrara VBB borehole station configuration and installation, with first results.
 
In flood modeling, many 1D and 2D combination and 2D models are used to simulate diversion of water from rivers through dyke breaches into the hinterland for extreme flood events. However, these models are too demanding in data requirements and computational resources which is an important consideration when uncertainty analysis using Monte Carlo techniques is used to complement the modeling exercise. The goal of this paper is to show the development of a quasi-2D modeling approach, which still calculates the dynamic wave in 1D but the discretisation of the computational units are in 2D, allowing a better spatial representation of the flow in the hinterland due to dyke breaching without a large additional expenditure on data pre-processing and computational time. A 2D representation of the flow and velocity fields is required to model sediment and micro-pollutant transport. The model DYNHYD (1D hydrodynamics) from the WASP5 modeling package was used as a basis for the simulations. The model was extended to incorporate the quasi-2D approach and a Monte-Carlo Analysis was used to conduct a flood sensitivity analysis to determine the sensitivity of parameters and boundary conditions to the resulting water flow. An extreme flood event on the Elbe River, Germany, with a possible dyke breach area was used as a test case. The results show a good similarity with those obtained from another 1D/2D modeling study.
 
Sensor Unit and Outdoor Electronics Unit of the classic tall (A) and low-profile 2DVD version (B) Sensor Unit and Outdoor Electronics Unit of the classic tall (A) and low-profile 2DVD version (B) . 
The 2D-Video-Distrometer (2DVD) is a ground-based point-monitoring precipitation gauge. From each particle reaching the measuring area front and side contours as well as fall velocity and precise time stamp are recorded. In 1991 the 2DVD development has been started to clarify discrepancies found when comparing weather radar data analyses with literature models. Then being manufactured in a small scale series the first 2DVD delivery took place in 1996, 10 years back from now. An overview on present 2DVD features is given, and it is presented how the instrument was continuously improved in the past ten years. Scientific merits of 2DVD measurements are explained, including drop size readings without upper limit, drop shape and orientation angle information, contours of solid and melting particles, and an independent measurement of particles&apos; fall velocity also in mixed phase events. Plans for a next generation instrument are described, by enhanced user-friendliness the unique data type shall be opened to a wider user community.
 
In many subduction zones in the world, low-frequency tremors and earthquakes have been recognized at a depth of about 30 km. They occur independently or migrate along the trench direction of the plate interface. We investigate behaviors of their patterns through numerical simulation, by varying frictional properties of the plate interface. Our simulation results indicate that a chain reaction of small asperities can reproduce the migration process in terms of the migration speedand the slip velocity, under the condition that characteristicslip distance is larger than 0.4 mm. © 2011 by World Scientific Publishing Co. Pte. Ltd. All rights reserved.
 
In autumn deep convection in the Mediterranean region is a common phenomenon. The local events characterized by deep convection are still a difficult task even for high resolution numerical weather prediction. Three flood cases, produced by convection either embedded in a large scale system or locally developed, occurring in Italy, are presented. All these case were not correctly forecasted: Sardinia (Cagliari, 13 November 1999); Calabria (Soverato, 7 September 2000) and Sicily (Catania, 16 September 2003). The first case occurred during the Mesoscale Alpine Programme (MAP) campaign, therefore a lot of data are available; for the second one only data from SSM/I and local rain-gauge are available; the third one occurred during the operational experimentation of the TOUGH project. The last one was not well predicted even using the operational assimilation of ground based GPS. To improve the forecast of these cases the assimilation of several data is tested. The variational assimilation performed using 3DVAR of GPS, SSM/I and surface and upper air data is applied to improve the Initial Conditions of the Sicily case. The Sardinia case is improved using either GPS and surface data, whereas for the Soverato case only ZTD is assimilated. The experiments are performed using the MM5 model from Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR); the model is initialized using the new Initial Conditions produced by the variational assimilation of conventional and non conventional data. The results show that the assimilation of the retrieved quantities does produces large improvement in the precipitation forecast. Large sensitivity to the assimilation of surface data and brightness temperature from SSM/I is found.
 
Model domains. The light gray dots are the SSM/I pixels selected by 3DVAR for Brightness Temperature or water vapor data assimilation; the dark gray dots are the points where the surface wind speed is available; the black points are the land and sea surface stations used to validate the data assimilation results on the Initial Conditions.
Initial Conditions (first column) and related experiments (last column).
1 hour observed accumulated precipitation (mm) from rain gauges ending at 16:00 UTC 20 September 1999.
Differences between surface stations and analysis for each case at the observation location for Temperature ( • C), and horizon- tal wind component U and V (m/s).
1 hour accumulated precipitation (mm) ending at 16:00 UTC 20 September 1999 for CNTR.
Data assimilation by 3DVAR of data from the Special Sensor Microwave/Imager (SSM/I) has been performed to study the IOP2b case (19-21 September 1999) of the Mesoscale Alpine Programme (MAP). Only data over the sea surface are used to avoid the contamination of the surface emissivity. Moreover, the rainy data are filtered out because the assimilation algorithm of 3DVAR does not take into account the scattering processes. SSM/I data are assimilated in two different ways: as Brightness Temperature directly, or as Precipitable Water and surface wind speed retrieved from the Brightness Temperature. The effect of the thinning of the observations has been studied and a set of sensitivity test cases has been carried out; the one by one removal of the SSM/I frequencies from the initial dataset allows to evaluate their impact on the Initial Conditions. A few experiments are performed using these new Initial Conditions to initialize the MM5 (PSU/NCAR) model. The results show that the assimilation of the retrieved quantities, i.e. Precipitable Water and surface wind speed, does not produces large improvement in the Initial Conditions. Vice versa, the assimilation of the Brightness temperatures produces a large variability of the Initial Conditions. The forecast experiments show that the model is very sensitive to the 22GHz and 37GHz frequencies.
 
(a) Wind speed winds estimated for a 100 years return period for ATLN, ALBO, LEON, SICI, BORA, EGEN and EGES regions – (b) Differences between the 100 years return period wind estimated by means of the standard approach and the regional frequency analysis. 
The present contribution addresses the performance of a statistical extreme wind analysis over the whole Mediterranean Basin. Estimations of return periods and levels are obtained over offshore areas through analysis of annual wind maxima. An alternative regional statistic method, based on regional L-moments, is also proposed. This regional technique allows increasing the sample size, using data from a homogeneous region instead of only from a single location, reducing therefore uncertainty. The performed statistical extreme wind analyses provide a detailed assessment of Mediterranean offshore high wind areas.
 
The maximum deepening rate per cyclone track is determined by the maximum height drop at the center of the cyclone (500-hPa low) on the basis of all the 6-h successive steps in its life cycle. The geopotential height gradient is calculated over the entire low area and the calculation continued with the variation of the gradient in the successive steps. The maximum intensification rate per cyclone is then determined as the maximum increase of the gradient in the life cycle. Maximum deepening rate for the 500-hPa cyclones in the area does not exceed, on average, 12 gpm/6 h. Maximum intensification which is 1.4 gpm/100 Km*6 h on average, occurs in the early stages of the cyclone&apos;s life cycle. This on the average happens approximately 9 h after the first time the low is detected. At the gulf of Genoa and the Adriatic Sea, cyclones usually show the maximum intensification after the maximum deepening. At Turkey&apos;s cyclogenesis area, however, this order is reversed. The spatial distributions of maximum intensification in the three sub-periods, indicate that it mainly occurs over Seas during late warm periods and over land during early and middle warm periods. Such a behavior underlines the role of low-level instability in cyclone development.
 
The juniper (Juniperus Sibirica Burgsd) tree-ring chronology with 20-year running mean from the Kola Peninsula (67.77 • N, 36.52 • E), 1328-2004.
The same as in Fig. 2, but for St.-Petersburg temperature (60.0 • N, 30.3 • E), 1752-2002.
It is generally believed that the low-frequency variability of climatic parameters seems to be connected to solar cycles. The principal periodicities are: 11-year (Schwabe), 22-year (Hale), 33-year (Bruckner) and 80–100-year (Gleissberg) cycles. The main heliophysical factors acting on climate, the biosphere and the atmosphere are solar irradiance, the intensity of solar and galactic cosmic rays (relativistic charged particles with energies >500 MeV) changing the cloud cover of the atmosphere, and UV-B-radiation. The 11-year and 80–90-year solar cycles are apparent in solar radiation and galactic cosmic ray trends. At the same time the bidecadal Hale cycle, related to a reversal of the main solar magnetic field direction is practically absent in either solar radiation or galactic cosmic ray variations. Besides, nobody can identify any physical mechanisms by which a reversal in the solar magnetic field direction could influence climate. However, the 22-year cycle has been identified in rather many regional climatic (droughts, rainfall, tree growth near 68° N, 30° E) and temperature records all over the world. We discuss here three possible cause of the bidecadal periodicity in climatic records, one of which is associated with a variation of stardust flux inside the Solar System. The most recent observations by the DUST experiment on board the Ulysses spacecraft have shown that the solar magnetic field lost its protective power during the last change of its polarity (the most recent solar maximum), so that the stardust level inside of the Solar System has been enhanced by a factor of three. It is possible that the periodic increases of stardust in the Solar System may influence the amount of extraterrestrial material that falls to the Earth and consequently act on the Earth's atmosphere and climate through alteration of atmospheric transparency and albedo. This material (interstellar dust and/or cometary matter) may also provide nucleation sites and thereby influence precipitation.
 
Different types of anomalous tropical cyclone tracks (After South China Typhoon Research Committee, 1977, 1978). Four digit numbers are time. 
2. The spatial distribution of anomalous tropical cyclone tracks in 5 strongest El Niño (top) and 5 strongest La Niña (bottom) events over the Western North Pacific Ocean Basin, 1958-98.
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The abruptly recurving tropical cyclones over the Western North Pacific Ocean Basin during El Niño and La Niña events are studied. Temporal and spatial variations of these anomalous tracks under different phases of ENSO are shown. The anomalies of the pressure field in relation to ENSO circulation for the occurrence of the abruptly recurving cyclone tracks are investigated using fuzzy method. These are supplemented by wind field analyses. It is found that the occurrence of recurving-left (RL) and recurving-right (RR) tropical cyclones under the modification of the steering currents, including the re-adjustment of the westerly trough, the expansion or contraction of the sub-tropical high pressure, the intensifying easterly flow and the strengthening of the cross-equatorial flow, can be in El Niño or La Niña events. Evidently, there is a higher chance of occurrence of anomalous tropical cyclone trajectories in El Niño rather than La Niña events, but there is not any pronounced spatial pattern of anomalous tropical cyclone tracks. By analyzing the pressure-field, it is seen RL (RR) tropical cyclones tend to occur when the subtropical high pressure is weak (strong) in El Niño and La Niña events. More importantly, how the internal force of tropical cyclones changed by the steering current, which relies upon the relative location of tropical cyclones to the re-adjustment of the weather systems, shows when and where RL and RR tropical cyclones occur in El Niño and La Niña events.
 
Top-cited authors
Maria Carmen Llasat
  • University of Barcelona
Silas Michaelides
  • The Cyprus Institute
Montserrat Llasat-Botija
  • University of Barcelona
Yoav Yair
  • Reichman University
Federico Porcu
  • University of Bologna